Recently, the nonlinear second-order topological phase has been studied in
photonics[1]}. We proceed to study the case where the matrix \(M_{nm}\) 
describes the breathing Kagome lattice, whose lattice structure is
illustrated in Fig.REF (b). The matrix \(M\)  in the momentum
space is given by[2]}
\(M\left( \mathbf {k}\right) =-\left(\begin{array}{ccc}0 & h_{12} & h_{13} \\h_{12}^{\ast } & 0 & h_{23} \\h_{13}^{\ast } & h_{23}^{\ast } & 0\end{array}\right) , \) 
